Windows

I think the main think is memory, use a PC with 2GB of RAM so at least 1/2 can be used for virtual machine.
Also, I would turn off the graphical enhancement stuff such as Aqua to improve performance.
I tried it on a 1GB host machine and it was too slow to be usable.

I use Vista in a VMWare 6 WS session a ton, and I can give you this:

1. It is about 20% slower than a comparably equipped PC. That is to be expected, as XP, Linux, or 2K would do the exact same thing due to VMWare overhead.

2. Do try to use a workstation that you can dedicate 1GB of RAM to. I use it in 512MB, but it is a bit slow. (remember that w/512MB on a "real" PC, it would be a bit sluggish as well.)

3. You won't get Areo in the VMWare session. Just won't happen as the virtualized Video adapter is not DirectX 9 compliant.

4. Try to use a dual-core processor machine as the host. VMware allows you to use one or both processors. Dedicate one to it, and your performaance should be acceptable. I allow mine to use both processors, but I'm not doing Autocad on the host machine.

5. YMMV. Depending oon what you're running in the host, you may get better or worse performance from the VM.

6. Set the host OS to give priority to background tasks rather than programs. That can make a huge difference.

7. Defrag the HDD before AND after installing Vista. Vista w/Office and some associated apps can take 8GB of HDD space or more, so defragging can be a big difference maker.

Note that most of these tips apply to any VM. Not just Vista. Understand the 20% performance hit on like hardware vs virtual, and you should be fine.

Good luck!